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Static axial overloading primes lumbar caprine intervertebral discs for posterior herniation
Cornelis P L Paul1, Magda de Graaf1, Arno Bisschop1
1Department of Orthopaedic Surgery, VU University Medical Center, Amsterdam Movement Sciences, The Netherlands.
Plos One
|April 7, 2017
Summary
Static overloading of the lumbar intervertebral disc (IVD) particularly damages the posterior annulus, increasing the risk of herniation. Dynamic overloading affects all IVD regions, impacting cell viability and matrix integrity.
Area of Science:
- Biomechanical Engineering
- Orthopedic Research
- Cellular Biology
Background:
- Lumbar intervertebral disc (IVD) herniations commonly occur in the posterolateral region, with mechanical loading identified as a key risk factor.
- Previous research indicates that dynamic and static overloading differentially impact the nucleus and annulus of the IVD.
- This study investigates regional mechanical and cellular responses within the lumbar IVD to dynamic and static overloading, hypothesizing variances that explain posterolateral herniation predilection.
Purpose of the Study:
- To assess the regional mechanical and cellular responses of lumbar caprine discs to dynamic and static overloading.
- To determine if differential responses in anterior, lateral, and posterior annulus regions explain the posterolateral herniation.
- To elucidate the impact of overloading on IVD height loss, pressure transfer, cell viability, and matrix integrity.
Main Methods:
- 125 lumbar IVDs were cultured in a bioreactor and subjected to simulated-physiological loading (SPL), high dynamic (HD), or high static (HS) overloading.
- Loading effects were analyzed across five disc regions: nucleus, inner annulus, and anterior, lateral, and posterior outer annulus.
- Measurements included IVD height loss, external pressure transfer, cell viability quantification, and matrix integrity assessment.
Main Results:
- Overloaded IVDs exhibited significant height loss, though axial pressure distribution remained consistent.
- High dynamic (HD) overloading led to cell death and matrix disruption across all IVD regions.
- High static (HS) overloading predominantly impacted cell viability and matrix integrity in the posterior outer annulus.
Conclusions:
- Axial overloading is detrimental to the lumbar IVD, with static overloading posing a greater risk to the posterior annulus.
- The nucleus appears relatively protected from static overloading.
- These findings suggest static overloading predisposes the disc to posterior herniation, with implications for occupational health and degenerative disc disease interventions.